Magneto



Jan. 10, 1933.

J. F. MARTIN MAGNETO Filed Feb 26. 1931 2 Sheetsheet 2 ATTFRNEY Patented Jan. 1o, 1933 UNITED STATES PATENT OFFICE JOHN F. MARTIN, 0F SPRINGFIELD,\ASSACHUSETTS, ASSIGNOR T0 UNITED AMERICAN :BOSCH CORPORATION, OF SPRINGFIELD, MASSACHUSETTS, A CORPORATION OF NEW YORK MAGNETO Application mea February 26, 1931. serial m. 518,484.

This invention relates to improvements in magnetos, especially magnetos for generating electric current to ignite the fuel charges in the .power cylinders of internal combustion engines.

An object of this invention is to provide an ignition magneto of the inductor type to be associated with the flywheel of the engine and controlled thereby.

Another object of the invention is to pro- .vide an ignition magneto comprising a generating coil witha suitable source of magnetism, the flux from which is alternately conducted through the coil and diverted therefrom through a shunt or by-pass of variable magnetic reluctance. For this purpose a shunting element is mounted. upon the flywheel of the engine in 'position to cooperate with they rotor of the magneto by bridging and exposing in succession the pole pieces of said magneto.

A further object of this invention is to provide such a magnetowhich is of small size and low cost which does not materially add to the weight of the engine and which is of high eflciency and `simple construction.

An additional object is to provide an ignition magneto of the above mentioned type comprising a relatively small number of parts but compactly arranged and capable of delivering a sufficiently strong current to give a satisfactory spark.

The nature and advantages of the invention are fully set forth in the following descrip- 'tion and drawings that illustrate the preferred form of the invention. But while a practical embodiment is shown in the drawings, variations in shape, size and arrangement of the various members may be adopted without departing from the principle of the invention'or exceedingthe scope of the appended claims.

On the drawings, i

1 is a front view of a magneto according to the invention; Fig. 2 is a transverse aial section showing the magneto and flywheel assembled; Fig. 3 is a diagrammatic view showing the shunting element carried by -the flywheel and how this element cooperates with the. polepieces; and Fig. 4 is avfront view of the polepiece which carries the generating windings of the magneto.

The same numerals identify the same parts throughout.

In the detailed description of the drawings, the numeral 1 is employed to indicate-a circular support which has the, form of a dished plate to be mounted in stationary position on any convenient part of the e11- gine. This support carries the permanent magnets 2, the polepieces 3 and 4, the generating coils 5, and the circuit interrupter or breaker 6. These parts are attached to the concave face of the plate l. The support 1 has a central opening 7 for the main shaft 8 of the engine, upon which is rigidly secured the rotor 9, the actuating member 10 for the breaker 6, and the flywheel 11. The flywheel has a hub 12 keyed to the shaft 8, and a circumferential flange 13. The flywheel 11 also carries a shunting element 14 of magnetic material to bridge the space between the polepieces for a purpose to be eX- plained later. -The rotor 9 has a recess 15 in its circumference, and in the operation of themagneto the rotor withits recess 15 co- 'acts with the element 14 to control the magnetic flux through the coils 4.

The plate 1 has a plane rim 16, and on the concave face of this plate are projections 17 to which the magnets 2 and the polepieces 3 and 4 Iare affixed. Both polepieces a-re laminated, the former comprising central laminations 18 between side laminations 19. The laminations of both polepieces 3 and 4 have recesses 20 (see Fig. 3) at the top to receive the ends of the magnets 2. On the polepieces 3 are outside laminations or4 covers '21, and

vbolts or rivets 22 bind all the laminations together. Adjacent. the coil 5 the polepiece 3 is relatively thin; that is, the lamlnations are somewhat narrow, and along the end of the coils remote from the rotor 9 the polepiece 3 has a straight edge 23, eatending along part of the side of the olepiece, the other side being curved according to the radius of the plate 1. The laminations 19 are all of this shape, but the middle laminations 18 extend out towards the rotor 9, forming a horn o r polar projection 24 to carry the coils 5,' this projection being of course less thick than the remainder of the polepiece 3, and its outer serve as covers for the laminations 18, in-I cluding the projection 24. Screws 26 (not shown in Fig. 2) hold the polepiece 3 fast to the. support l. The laminations of the polepiece 4 are all of the same shape, as indicated in Fig. 1, and this polepiece extends from the opposite ends of the magnets 2 towards the rotor 9 as straight as possible to limit the length of the ma netic circuit through the coils 5. Its polar ace, however, is somewhat longer than the polar face of the projection 24.

If desired, the outside cover 21 of the polepiece 3 may be bent over as shown at 27, and likewise the outside cover or lamination of the polepiece 4, to press against the tops of the magnets 2. Each part which is thus bent provides a tab which holds the magnets securely in case the magnets titwith any' slight looseness in the recesses 20.

There will now be described the design of the interrupter 6. At one point the plate 1 has a plane section 28, which is an inward extension of the plane rim 16, and to the face of this section presented to the iiywheel is made fast the condenser 29, held in place by a metal clip or strap 30. On the same face of the section 28 is a small shelf 31, on which is a metal contact strip 32 between insulating strips 33. This strip is made fast by bolts and" nuts, and the apertures for the bolts through the strip 32 may be larger than the thickness of the bolts, so that the strip will not be united electrically by the bolts to the shelf 31. At the end of the strip is the fixed terminal 34. v

Secured to the section 28, further, is a stud 35, in a bearing 36. The stud has a th'ckened collar 37 abutting this bearing, and on the outer face of the section 28 the lstud carvries a washer 38 against which the extremity of stud is riveted to hold it fast. Above the shelf 31 the stud carries a flange 39 between which and the collar 37 is the breaker lever 40. This lever is curved at 42 so that it passes beneath the stud 35, and is pressed up against it. The lever 40 bears the movable terminal 41, which is normally in engagement with the terminal 34. The opposite end 43 of the lever is turned up towards the shaft 8, to be operated by the strker or cam yblock 44 on the member 10. A spring 45, atlixed to the bottom of the shelf 31 by the bolts and nuts holding the strip 32 engages the lower face of the lever at its other end and presses it upward about the stud 35 as a pivot or fulcrum, to keep the terminal 41 in contact with the terminal 34.

The coils 5 include a primary and a secondary, the former being grounded at 46 on the polepiece 3, and connected at its opposite end by conductor 47 to the condenser 29. The opposite pole of this condenser is also grounded, but the pole to which the conductor47 is joined is also united to the strip 32 by a short conductor 48. The lever 40 is also grounded, and to ensure an efficient ground connection, a shortlength of conductor 49 jo'ns this lever to the shelf 31. At 50 is the high tension lead of the secondary winding of the coil 5, passing out through an insulated bushing 51 in the plate 1.

The striker or cam 44 may consist of laminations of fiber or other suitable materfal, secured to the member 10 by rivets. This member isafxed to the rotor 9 so that it can be adjusted. It has the form of a ring with elliptical slotsr52, through which are passed screws or bolts 53. The ring can be turned angularly by loosening the bolts and rotating the ring as permitted by the slots 52, and then tightening the bolts 53.

A cover or case 54 may be tted over the breaker inside of the flywheel and the support l, and this cover can be held in place by screws passing through perforated ears 55 on said cover, the screws entering threaded holes in the section 28. The bosses 56 may also be formed with threaded holes on the plate -1 so that it can be secured in operatvo position.

In operation the rotor 9, as it revolves forms a path of high magnetic permeabilily between the polepiece 4 and the projection 24 of the polepiece 3. So long as t-he recess 15 does not come into positon adjacent the projection 24, the iux from the permanent magnets 2 threads through the coils 5 by way of the polepieces 3 and 4 and the rotor 9. When, however, the rotor 9 carries the recess 15 towards the projection 24, the arc-shaped rib or shunting element 14 on the flywheel 1l is carried into position to bridge the upper ends o f the polep'feces, and when the recess 15 is fully in line with the projection 24, the shunting element 14 will be in central bridging position with respect to polepieces 3 and 4. The magnetic'flux wfll now be diverted from the coils and rotor 9 in large measure and by-passed through the element 14. The shunt path established by the element 14 is of variable reluctance, because, if .the direc-- tion of rotation be taken as clockwise with respect to Fig. 3, the element 14 will first arrive at the polepiece 3, and as it passes on above the magnets 2 towards the polepiece 4, the reluctance of the by-pass becomes less and less. Hence, as the recess l5 on the rotor 9 is now coming more and more into line willi the projection 24, the flux through the coils 5 diminishes in intens'ty, and increases through the element 14. the striker or cam block 44 on the member 9 At this time also hits the interrupter lever 40 and separates the terminals 34 and 41.' A high tension current is then induced in the secondary winding and lflows out through the lead 50. Further rotation ofthe rotor carries the cam block 44 past the interrupter; the terminals 34 and 41 again come together, and simultaneously therecess 15 in the rotor 9 is carried past the projection 24, and the element 14 carries its trailing end away from the polepiece 3 while its leading end revolves past the top of the polepiece 4. The magnetic flux now builds up again in coils 5 in preparation for the next spark.

The'magneto, built a's described, iscomparatively light and `easily assembled, yet makes a very durable structure. .A strong spark is always given and if at any time inspection-or repar is needed, access to the magneto can be had simply by drawing the flywheel off the shaft 8, and if the magneto then has to be dismounted, it is only neces- `sary to remove the fastening bolts from the bosses 56.

Having described the invention, what is believed to be new, to be secured by' Letters Patent of the United States is:

1. A magneto comprising generating coils, a source of magnetic flux for said coils, a pole piece associated with each pole of said source and having opposed `polar faces, said coils being mounted on one of said pole pieces between the polar face thereof and said source, a rotor shaped to vary the permeability of the magnetic path through said coils, the rotor being disposed between said polar faces, and a shunting element to form a path of changing reluctance through which magnetic Hux is diverted from said coils.

2. A magneto comprising generating coils, a source of magnetic ux therefor, a pole piec associated with each pole of said source and having opposed polar faces, said coils being mounted on one of said pole pieces between the polar face thereof and said source, a rotor to control the passage of flux from said source through said coils, a iiywheel, the rotor being disposed between said polar faces, and a shunting element on the flywheel to provide a path of variable reductance through which magnetic flux is diverted from said coils.

3. A magneto comprising a fixed support carrying generating coils7 a source of magnetic flux, pole pieces having o posed polar faces connected to each pole o said source, said coils being mounted on one of said pole pieces between the polar face thereof and said source, and a circuit breaker, an engine shaft a rotor von said shaft disposed between said polar faces, a flywheel on said shaft having a rim encircling said support andthe parts 'of the magneto attached thereto, and a shunt- 4. A magneto comprising a support, magnets attached to said support, polepieces at the ends of themagnets, one of said polepieces having a projection, said projection and the other pole piece having opposed polar faces, generating coils on said projection, a rotor between the polar faces to control the iux from said magnets through said coils, a circuit breaker on said support for said coils, a cam block on the rotor to actuate the circuit breaker, and a flywheel having a shunting element movable with the rotor to divert magnetic flux from said coils.

5. A magneto comprising a stationary support, a source of magnetic flux secured to the support, a laminated pole iece atone end of said source of magnetic nx, a polepiece at .the opposite end of said source, said second named polepiece comprising middle laminations amd outside laminatlons, the middle laminations having lateral projections extending toward the first polepiece, generating coils on said projections and a rotor to control the flux throughsaid coils.

6. A magneto comprising a dish-shaped .supportl adapted to be mounted in stationary position upon an internal combustion engine,

with its convex face turned towards said engine, magnets fixedto the concave face of said plate, polepieces at the end of said magnets, enerating coils mounted on one of the polepieces, said support having an outturned plane rim, the support also having a plane section forming an inward extension of said rim diametrically opposite said magnets, a circuit interrupter comprising a xed and a movable terminal mounted on said section, a rotor between said polepieces and between saidmagnets and said circuit interrupter to control the magnetic flux through the coils, a cam on the rotor to actuate the circuit 'interrupten a shaft for said engine to which the rotor' is attached, a hollow iiywhee'l on said shaft with an axially extending flange enveloping said support and the parts of the magneto thereon, anda shunting element carried by said flywheel to divert magnetic flux from said coils.v

7. `A magneto comprising generating coils, a source of magnetic flux therefor, said source `having a pole piece on which said coils are mounted, a rotor to control the passage of said ux through said coils, a circuit breaker for said coils, an actuating memberl for the circuit breaker attached to said rotor, said member comprising a ring with elliptical slots therein, a striker block attached to the ring and screws to pass through such slots and adjustably secure said ring to the rotor. Y

8. A magneto comprising a support, magnets thereon, polepieces at the end of the magnets, generating coils on one of the polepieces, a circuit breaker for said coils comprising a fixed and a movable terminal, said support having ashelf to which the fixed terminal is insulatably attached and a stud adjacent said shelf forming a fulcrum, a lever bearing the movable terminal engaging said stud, a spring attached to the shelf and pressing against the lever to hold said terminals in contact, a rotor to control the magnetic flux and an actuating member for said lever.

9. A magneto having a source of'magnetic flux, generating coils, the source having a pole piece on which said coils are mounted, means to control the fluX, a Circuit breaker for said coils, and an actuating member for said circuit breaker, said member comprising a ring with elliptical slots for the passage of screws to secure said member in adjustable position.

10. A magneto comprising a dished support having a plane section, a shelf projecting therefrom, a stud projecting adjacent the shelf, a lever engaging said stud as a fulcrum, a terminal on the lever, a terminal insulatably secured to said shelf, a spring engaging the lever so as to hold said terminals in contact, an actuating member for said lever, generating coils on said support controlled by said circuit breaker, magnets on said support, and a rotor to controlthe flux of said magnets through said coils.

11. A magneto comprising magnets forming a source of magnetic flux, pole pieces and generating coils, the source having a pole piece on which said coils are mounted, and a flywheel having a flange enveloping said magnets, polepieces, and coils, said flywheel having an arc-shaped rib projecting from one side thereof to form a shunt for bridging the polepieces and diverting flux from said gen-g4 erating coils. v

12. A magneto comprising a support, magnets with polepieces and generating coils mounted on said support, said coils being carried by one of said pole pieces, a projection on said support for carrying a fixed contact connected to said coils, a stud on said support providing a fulcrum, an interrupter lever pivotally engaging said fulcrum to cooperate with said fixed contact, and a rotor for said magnets and said polepieces, said rotor 'comprising a striker member to actuate said interrupter lever.

13.,A magneto comprising generating coils, a source of magnetic flux therefore, said magneto having a pole piece on which said coils are mounted, said pole piece being connected to one pole of said source, a vpolepiece connected to the opposite pole, said. pole pieces having opposed polar faces, a rotor between said pole pieces to control said flux and a movable shunt element to provide a path of variable reluctance through Which the flux is diverted from said coils.

14. A magneto comprising generating I coils, a source of magnetic flux for said coils,

said source having a pole piece on which the 

